The present invention relates to an anti-copying system for audio signals, in particular digital audio signals.
Present day digital techniques allow perfect copies of audio signals to be made. For example, the digital audio information of a compact disc (CD) can be digitally registered on tape or can even be used to physically reproduce the CD by means of a so-called CD burner (recorder for compact discs). The possibility of digital copying, producing perfect copies of the original, has resulted in many illegal copies of CDs or other information carriers being made. This in turn leads to a substantial loss in copyright royalties. For this reason, there is a need for protection against copying of audio signals.